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La Jolla’s signature fireworks show should go off as planned on July Fourth, despite a third year of heated debate about whether such events damage the air, water and wildlife.

Opponents want San Diego city officials to investigate the full range of potential problems. It’s not clear if that will ever happen because the city is appealing three related court rulings, but an emerging series of scientific reports suggest fireworks aren’t entirely benign.

Whether the fallout is enough to force changes to occasional fireworks shows or the composition of aerial explosives is the central question. Answers likely will hinge on science, perceptions of risk and personal values — from Mission Hills residents tired of summertime pyrotechnics at SeaWorld to families from East County who look forward to visiting the coast for annual Fourth of July festivities.

Over the past year, 25 event organizers in the region have filed for pollution permits to discharge roughly 25,000 pounds of explosives over waterways, mostly Mission Bay and San Diego Bay.

So far, SeaWorld San Diego is the only group that must do water monitoring under the regional permit issued in May 2011. Those results, expected to be reported by the end of the year, will help local regulators decide whether to require more extensive assessments and it may help officials elsewhere decide whether to follow San Diego’s permitting path.

“We are still collecting information,” said Michelle Mata, an engineer at the San Diego Regional Water Quality Control Board. “It seems that people would want to see monitoring results before they move forward.”

So what kinds of ecological threats do fireworks pose?

There’s some concern about garbage related to duds and debris, but scientific inquiry has focused on the long list of additives that produce colors and explosive effects in fireworks. They include aluminum, barium, cesium, lithium, sulfur and titanium.

Related research is emerging around the globe, along with efforts to develop more environmentally friendly pyrotechnics for civilian and military use:

• A 2008 study linked an 18-fold increase in concentrations of perchlorate in precipitation samples to Independence Day shows in New York. Perchlorate is a widespread water contaminant that has been linked to thyroid disorders. A 2007 study showed a perchlorate spike of 1,000 times baseline levels in an Oklahoma lake after a pyrotechnic display.

• Atmospheric pollution by radium from fireworks can create “negative health effects” for people who inhale the “potential radioactive hazard,” said a 2009 study out of the Vienna University of Technology. Research in Italy found that fireworks are a “huge source of gaseous pollutants such as ozone, sulfur dioxide and nitrogen oxides” but also acknowledged that they “unlikely pose a significant health hazard.”

• The San Diego regional board said water monitoring near SeaWorld showed elevated pollutant levels after major fireworks shows. Pollutants such as arsenic, copper, mercury, tin, zinc and phosphorous were detected at levels above water quality criteria or higher than other spots, according to a 2011 report. It also said related sediment monitoring for metals “provides an indication of an accumulation of pollutants over time within the fireworks fallout area.”

But the agency acknowledged that it’s difficult to draw any conclusions about the level of actual ecological harm from Sea World’s pyrotechnics, and park officials maintain there’s no damage.

Despite such debate, the water board set a national precedent last year by requiring a “minor discharge” pollution permit for fireworks over bays, rivers, lakes and other waterways. Related research is supposed to better define the movement of pyrotechnic particles through the environment.

In addition, the Coastal Environmental Rights Foundation in Encinitas is pushing San Diego to review fireworks shows under the California Environmental Quality Act, or CEQA — a measure the city is fighting in court.

Foundation lawyer Marco Gonzalez said the CEQA review is important because it would be much broader than assessments by the regional board, which focus on water.

“CEQA requires consideration of alternatives, disclosure of impacts and mitigation of impacts when feasible, that doesn’t necessarily happen in the (water board) context,” Gonzalez said. “Further, the Clean Water Act … doesn’t deal with marine mammals. It doesn’t deal with birds. It doesn’t deal with air quality. It doesn’t deal with noise.”

So far, neither the State Water Board nor other regional boards around California have followed San Diego by mandating pollution permits for fireworks over water, meaning the issue might not have the regulatory reach that some initially anticipated. Nor has the issue caught fire across the country, said Robert Blake, president of the National Fireworks Association. “We haven’t heard anything anywhere (about environmental regulations) except in San Diego,” he said.

Blake said manufacturers have tried to use less-toxic chemicals when possible, but he doesn’t see it as a big issue. “The time of the exposure to the small amounts of chemicals that are there … is very minimal,” he said. “Most of the chemicals are burned up during the explosions.”

Even so, there’s been interest worldwide in developing environmentally friendly fireworks. Organizers of the La Jolla show said they have looked into perchlorate-free fireworks and found that they don’t come in as many colors as they wanted. But officials in India reportedly have turned to smokeless firecrackers to celebrate Diwali, and the U.S. Department of Defense has sponsored efforts to develop eco-friendly alternatives for signal flares — all part of the larger movement to minimize the spread of pollutants.